This application claims the priority of German application 197 57 865.9, filed in Germany on Dec. 24, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a hydraulic control unit having a housing made of light metal and connection devices for a connection with hydraulic conduits.
Hydraulic control units consist of a housing on which additional hydraulic devices, such as valves, filters, etc. are held. The housing has the task of guiding the flows of the hydraulic fluid; for this purpose, conduits in the form of grooves are provided in the housing. For the connection with the device to be controlled, such as a vehicle transmission, it is usually provided that the control unit is placed directly on the device to be controlled and the hydraulic connection is established by corresponding openings in a flange surface. Usually, beyond these internal connections, external connections are provided, as, for example, for the supply with hydraulic fluid and outflows to external hydraulic apparatuses which are also to be acted upon by the control unit.
For reasons of weight and for an easier manufacture and machining, the housings for such control units are usually made of a light metal. The problem arises in the area of the external connection devices that during the mounting of the external connections comparatively high forces, such as tightening moments in the case of screwed connections, must be applied in order to securely seal off the connection with respect to the hydraulic pressure. However, specifically in light-metal housings, the forces at which the housing is damaged, for example, by the tearing of a thread, are only slightly above the forces required for the sealing. In particular, the forces resulting in damage can easily be applied manually. Such damage will then also result in damage to the very expensive housing of the control unit and the housing must be repaired or replaced at high expenditures.
In view of this state of the art, it is an object of the invention to reduce the danger of damage to the housing in the area of the connection devices.
According to the invention, this object is achieved by providing a steel plate held on a flange surface of the control unit, which steel plate accommodates the connection devices. It is suggested that a plate made of steel be provided for receiving the connection devices, which plate is held on a flange surface of the housing. In contrast to the housing made of light metal, the steel plate is significantly less sensitive to damage because the forces necessary to result in damage are much higher. Should damage nevertheless occur during the mounting of the connection devices, the steel plate must only be exchanged, while the control unit itself must not even be demounted so that this exchange can take place particularly rapidly and at low cost.
It is suggested that in the plate for receiving the connection devices, bores with threads be provided which correspond to conduit bores of the housing arranged in the flange surface. In this application, the advantages of the invention are particularly noticeable since, especially in the case of a screwed connection in the area of the connection devices, the danger of damage caused by an excessive tightening moment is particularly high.
It is also suggested to provide a seal between the steel plate and the flange surface in order to avoid a flowing-out of hydraulic fluid in the area of the flange surface. Such a seal may, for example, be constructed as a shaped seal inserted into the steel plate, as a flat seal placed onto the plate or in the form of inserted O-rings in the area of the conduit bores.
If the conduit bores are to accommodate insert valves in the flange surface, it is also provided that the plate simultaneously forms the abutment for these valves. Such an abutment will for example, be required when the valve insert is constructed as a prestressed return valve and therefore a spring arranged on the return valve must be supported for applying the prestressing force.
Finally, it is suggested to provide projections laterally on the plate which rest on lateral surfaces of the flange surface. By means of this shaping of the plate, the torques introduced into the plate during the mounting of the connection devices can be supported in a form-locking manner so that this stress must not be absorbed by the fastening devices of the plate. A preferred application field of the invention are hydraulically actuated vehicle transmissions.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.